1. Field of the Invention
The present invention relates topolyorganosilsesquioxane and a process for preparing the same, and more particularly, to polyorganosilsesquioxane having silane-based compounds as starting materials, and a process for preparing the same.
2. Description of the Related Art
With the development of high-level advanced technology, research into high-performance, multi-functional high-technology materials is being conducted in various fields. In particular, in research into novel polymeric materials, much attention has been paid to novel high-functional organic polymers, e.g., organic polymers having improved heat resistance and glass transition temperature (Tg), and technology of forming organic or inorganic hybrid materials, such as an organic and inorganic hybrid complex.
There are known many existing organic or inorganic hybrid materials. In particular, due to importance of thermal stability between organic polymer and inorganic polymer, keen attention is focused on polyorganosilsesquioxane, which is a high-heat-resistance polymer.
Polyorganosilsesquioxane was first introduced in an article of J. Am. Chem. Soc., 82, 6194 (1960) by Brown et al., and commercialized in trade names of xe2x80x9cGlass-resinxe2x80x9d and xe2x80x9cSST-resinxe2x80x9d by Owens Illinois and Gelest. However, polyorganosilsesquioxane is not being put into practical use as industrial material because of difficulties of controlling the polymer structure and adjusting the molecular weight thereof.
A highly regular ladder form of polyorganosilsesquioxane accounts for its improved performance properties. Thus, along with development of novel starting materials that can easily form a perfect ladder-form structure, research into condensation methods thereof has been made in various fields of industry in various ways.
Among known methods of preparing polyprganosilsesquioxane, a representative method is to dehydrate and condense a precursor hydrolyzed product (oligomer), synthesized by hydrolyzing trichlorosilane or trialkoxysilane in the presence of alkali/acidic catalyst, thereby easily obtaining a low-molecular weight polymer (having a number-average molecular weight (Mn) of 10,000 to 30,000 and a degree of dispersion (Mw/Mn) of 3 to 20.
A conventional method of preparing polyorganosilsesquioxane using trichlorosilane will first be described. Oligomer produced by co-hydrolytic condensation when hydrolyzing trichlorosilane, the oligomer having Mn of 1,000 to 2,000 and a polydispersity index value (PDI) of 2 to 5, has a complicated, diverse structure, compared to silanetriol which is a single structure. In the case of forming high-molecular weight oligomer, a three-dimensional network structure is easily formed by constructural deformity due to the presence of inter-hydroxy group, and the inherent structure of oligomer, having the following disadvantages: 1) The structure of produced polymer is uncontrollable; 2) It is difficult to adjust the molecular weight of produced polymer and to obtain high-molecular weight polymer; 3) The produced polymer loses high regularity, lowering solubility against solvent; and 4) Remaining low-molecular weight components may adversely affect the heat resistance and mechanical property of polymer.
A conventional process for preparing polyorganosilsesquioxane using trialkoxysilane is also advantageous from the viewpoint of handling convenience, such as controllability of a hydrolysis rate, compared to trichlorosilane. However, various studies reported that this process had the following disadvantages caused by the oligomer molecular deformity due to the presence of inter-hydroxy group, and by the presence of alkoxy group: 1) A polymer of a branch structure, rather than a ladder structure, is formed; 2) selection of catalyst used, amount of the selected catalyst, selection of reactant solvent, careful adjustment of pH of selected reactant solvent, and so on, are not easy to achieve; and 3) a three-dimensional network structure causes micro-gelation. These disadvantages may adversely affect preparation of highly regular silicon ladder-form polymer.
As described above, a great attention has been paid to polyorganosilsesquioxane and constant research into the same has been made.
According to known various synthesizing methods, e.g., a sol-gel method, a ring-opening polymerization method or an equilibrium polymerization method, and research into the structure of polyorganosilsesquioxane, condensation thereof is very complicated and versatile, so that the structure of polymer cannot be sufficiently controlled. Thus, even a product commercially available in the trade name of glass resin, also called T-type resin, cannot meet several requirements to be used as a novel industrial material, which becomes impediment to practical use.
Requirements of novel industrial materials using organic or inorganic hybrid materials are: a low dielectric constant of 2 to 3; excellent thermal stability such as a pyrolysis starting temperature of 400xc2x0 C. or higher; low hygroscopicity; a low thermal expansion coefficient; excellent gap filling capability; excellent bondability.
To overcome the above-described problems, the present inventors proposed polyphenylsilsesquioxane having high regularity and crystallinity, which cannot be controlled by conventional methods(sol-gel method), using high-purity organosilanetriol as a starting material, rather than oligomer having various molecular weights and structures.
However, there is still a need for polyorganosilsesquioxane having high regularity/crystallinity.
It is an objective of the present invention to provide a novel high-technology inorganic material having excellent properties through development of new precursors, and preparation method thereof, the precursors being: 1) easy in handling; 2) capable of adjusting the rate of polymerization; 3) capable of uniformly distributing hydroxy groups at both ends of polymer; 4) capable of introducing Rxe2x80x94SiO3/2 to the main chain of polymer with high regularity; 5) easily capable of adjusting the crosslinking structure of polymer, specifically, crosslinkablity or crosslinking density; 6) capable of facilitating chemical modification by spreading the structure of polymer; 7) easily capable of forming nano-sized pores in the backbone of polymer; and 8) capable of imparting high functionality and versatile properties to polymer.
To accomplish the above objective of the present invention, there is provided polyorganosilsesquioxane and a process for preparing the same.
Polyorganosilsesquioxane according to the present invention is a compound represented by formula 1: 
wherein R1 and R2 are independently a hydrogen atom, an unsubstituted or substituted aliphatic hydrocarbon group having 1 to 30 carbon atoms, an unsubstituted or substituted aromatic hydrocarbon group having 1 to 30 carbon atoms, an unsubstituted or substituted alicyclic hydrocarbon group having 1 to 30 carbon atoms, an unsubstituted or substituted silyl group having 1 to 30 carbon atoms, an unsubstituted or substituted allyl group having 1 to 30 carbon atoms, an unsubstituted or substituted acyl group having 1 to 30 carbon atoms, a vinyl group, an amine group, an acetate group or an alkali metal, and n is an integer of 2 to 300,000.
In the present invention, 1,3-diorganorsiloxane represented by formula 2 is provided as a precursor for preparing the polyorganosilsesquioxane represented by Formula 1: 
wherein R1 and R2 are as defined above, R3 is a hydrogen atom, a lower alkyl group, acetate, sodium or potassium, and X represents a hydrogen atom, a halogen atom, a hydroxy group, an amine group or a carboxy group.
The process for preparing the polyorganosilsesquioxane according to the present invention can be expressed in the reaction scheme 1: 
wherein R1, R2 and R3 are as defined above, and n and X are as defined above.
The step (A) of the reaction scheme 1 is a step for preparing the compound which is a precursor for preparing polyorganosilsesquioxane of the present invention, represented by Formula 1, the precursor represented by Formula 2. In step (A), a compound represented by Formula 4, e.g., trichloromethylsilane, and a compound represented by Formula 3, e.g., trimethoxyphenylsilane, which are used as starting materials, are reacted in the presence of acidic catalyst or without catalyst, thereby easily preparing various kinds of compounds represented by Formula 2.
The organic solvent used in the above reaction is not specifically limited as long as it can be generally used in the art, but THF, benzene, anisol, chlorobenzene, xylene, methylisobutylketone (MIBK), dimethylformamide (DMF), N-methylpyrrolidone (NMP), 1,4-dioxane, dimethylacetamicle (DMAC), acetone, or toluene is preferably used.
As the catalyst used in the above reaction, HCI, acetone, triethylamine, tin, pyridine, trichloroacetic acid or an acetic acid-amine complex catalyst is preferably used, and specifically, trichloroacetic acid is more preferably used from the viewpoint of reaction rate, temperature and yield.
The reaction temperature is preferably 30 to 350xc2x0 C., and the reaction time is preferably 1 to 300 hours.
The compound represented by Formula 2 obtained as a precursor, is polymeric-condensed in an organic solvent, as represented by the step (B) of the reaction scheme 1 by the conventional method, thereby obtaining the polyorganosilsesquioxane represented by Formula 1.
The polymeric-condensation method used in step (B) of the reaction scheme 1 is not specifically limited, and various methods including heating, light radiation, electron beam scanning, microwave radiation and the like may be used. In the case of adding a catalyst, a compound having a large value of n can be obtained.
The compound used in step (B) of the reaction scheme 1 is preferably in the range of 5 to 300 parts by weight, preferably 10 to 100 parts by weight based on 100 parts by weight of organic solvent. If the amount of the compound represented by Formula 2 is less than 5 parts by weight, the polymeric-condensation may be retarded or the reaction is not fully carried out, and if greater than 300 parts by weight, gelation may undesirably occur during reaction.
The catalyst used for facilitating the polymeric-condensation in step (B) of the reaction scheme 1, is not specifically limited, but at least one material selected from the group consisting of alkali metal hydroxides such as sodium hydroxide, potassium hydroxide or cesium hydroxide, amines such as triethylamine, diethylene triamine, meth-butylamine, para-dimethylamine ethanol, triethanol amine, or quaternary ammonium salts, and fluorides. The catalyst used for polymeric-condensation is preferably in the range of 0.001 to 5 parts by weight, more preferably 0.001 to 1 part by weight based on 100 parts by weight of the compound represented by Formula 2.
In particular, in the case of using alkali metal hydroxide as a catalyst, it is preferred that the compound represented by Formula 2 is hydrolyzed in advance to thus produce a hydrolyzed product and polymeric-condensation is then carried out.
The organic solvent used in step (B) of the reaction scheme 2 is not specifically limited, and an organic solvent having a boiling point of 100xc2x0 C. or higher, such as toluene or NMP, is preferably used.
In step (B) of the reaction scheme 1, the reaction temperature is preferably 50 to 350xc2x0 C., more preferably 100 to 200xc2x0 C. The reaction time is preferably 1 to 50 hours in the case of using a catalyst. In the case of not using any catalyst, the reaction temperature is preferably 150 to 350xc2x0 C., and the reaction time is preferably 1 to 200 hours. If the reaction temperature is out of this range, the efficiency of the polymeric-condensation cannot meet industrial requirement.
Also, if the purity of the compound represented by Formula 2 for polymeric-condensation, is greater than or equal to 90%, a high molecular weight polymer, that is, Mn greater than 500,000, can be obtained by the phase transition method.
The polyorganosilsesquioxane represented by Formula 1 according to the present invention has a high solubility to a general organic solvent, and is soluble in organic solvents including aromatic hydrocarbons such as toluene, xylene, benzene or chlorobenzene, hydrocarbons such as methylene chloride or chloroethane, ethers such as THF, 1,4-dioxane, diethylether or dibutylether, ketones such as acetone, methyethylketone or methyletherketone, esters, or dimethylformamide.
In the present invention, R1 and R2 are independently a hydrogen atom, an unsubstituted or substituted aliphatic hydrocarbon group having 1 to 30 carbon atoms, an unsubstituted or substituted aromatic hydrocarbon group having 1 to 30 carbon atoms, an unsubstituted or substituted alicyclic hydrocarbon group having 1 to 30 carbon atoms, an unsubstituted or substituted silyl group having 1 to 30 carbon atoms, an unsubstituted or substituted allyl group having 1 to 30 carbon atoms, an unsubstituted or substituted acyl group having 1 to 30 carbon atoms, a vinyl group, an amine group, an acetate group or an alkali metal, preferably a lower alkyl such as a hydrogen atom, a methyl group, an ethyl group or a propyl group, a phenyl group, a phenol group, a chlorophenyl group, vinyl group, carboxyl group, a trimethylsilyl group, acetate or alkali metal, and more preferably a hydrogen atom, a methyl group, a vinyl group or a trimethylsilyl.
As described above, according to the present invention, unlike in conventional polyorganosilsesquioxane obtained by heat-condensing oligomer prepared by hydrolyzing conventional trichlorosilane or triethoxysilane, a silane-based compound is first reacted as a starting material to obtain 1,3-diorganosiloxane, which is a precursor, and then polymeric-condensed to obtain polyorganosilsesquioxane, thereby synthesizing a highly-regular ladder-form polymer having repeating units of cyclotetraorganosilsesquioxane.
As described above, since Sixe2x80x94Oxe2x80x94Si bonds and ladder-form structures are easily formed in the main chain of polymer with high regularity, high-heat-resistance can be maintained. Also, since inter-hydroxy group structures or defects existing in the main chain of polymer can be reduced, no thermal treatment is required and various functional side chains (e.g., a photosensitive group or dealkyl reactive group) can be introduced. In particular, the physical property of polymer depending on a composition ratio of the introduced side chains, e.g., a difference in the ratio of phenyl to methyl, can be changed, and new polymeric molecules can be designed. Since terminal-silanol groups can be arranged regularly at the terminal of polymer so that the amount of organic polymer introduced can be adjusted in preparing organic or inorganic hybrid materials, thereby easily preparing an organic or inorganic copolymer.
In particular, the polyorganosilsesquioxane prepared according to the present invention has a unique molecular structure, that is, the ratio of siloxane (Sixe2x80x94Oxe2x80x94Si) bonds and rigid ladder-form structures (Rxe2x80x94SiO3/2) present in the main chain of the polyorganosilsesquioxane prepared according to the present invention is 97% more than in the conventional polyorganosilsesquioxane, the percentage being represented by
{No.of Rxe2x80x94SiO3/2)÷(No.of hydroxygroups+No.of terminalxe2x88x92silanol groups)xc3x97100}.
Thus, the polyorganosilsesquioxane prepared according to the present invention exhibits high solubility to a general organic solvent, and has excellent anti-wearability, low surface tension, optical transparency, low dielectric constant of 3.0 or less, low absorption ratio, excellent gap filling capability and so on. Also, the polyorganosilsesquioxane prepared according to the present invention is excellent in view of adhesion to glass or metal, e.g., aluminum, copper, titanium or silicon, electric insulation, water drainage, chemical resistance or transparency, by introducing different side chains, and can be commercially applicable in a wide range of industrial materials.
The polyorganosilsesquioxane prepared according to the present invention can be used in various fields: UV curable resins and silane compounds are widely used; and glass resins are also used in some fields. Materials of the polyorganosilsesquioxane prepared according to the present invention include polycarbonate, acryl resin, diethylglycolbisalkylcarbonate (in the trade name of xe2x80x9cCR-39xe2x80x9d) and so on. The polyorganosilsesquioxane prepared according to the present invention can be used for plastic, sunglasses, protective glasses, dash board, automobile lamps, aircraft windows or bulletproof glass. Also, the polyorganosilsesquioxane prepared according to the present invention can be used for thermally treating glass lenses with glass resin.
Further, the polyorganosilsesquioxane prepared according to the present invention is excellent in view of electric insulation, heat resistance, low absorption, planarization of a spin-on glass (SOG) solution, thereby being adapted to electronic usage. For example, the polyorganosilsesquioxane prepared according to the present invention is a general-purpose material that can be used as a protective coating for a thin film, an interlayer dielectric film in LSI multiple layer wiring, a low dielectric material, a multiple insulation film, an LCD insulator film and the like.
Recently, as a highly integrated semiconductor device has become narrower in line space, the thickness of formed coating layers unavoidably increase, resulting in cracks. Generation of cracks is presumably caused by the following factors: 1) thermal curing contraction stress generated when inter-hydroxy groups or terminal-silanol groups are mutually condensed; and 2) a difference in thermal stress depending on a difference in the thermal expansion coefficient among a cured film, an aluminum wiring and a silicon wafer. In the present invention, since the presence ratio of inter-hydroxy groups is low due to a defective structure of polymer, that is less than or equal to 5%, a reaction occurring at the terminal can be prevented by introducing silylation or double bond into the terminal-silanol group, and new functionality of an organic-inorganic hybrid material can be attained by introducing other organic polymer, specifically polyimide, polyamide, PMMA, polyacryl, polycarbonate, polystyrene or polyurethane.
Further, the polyorganosilsesquioxane prepared according to the present invention is soluble in various solvents to form a thin film easily and has a high level of hardness of 4 to 8H. Also, since the polyorganosilsesquioxane prepared according to the present invention can form a highly transparent thin film, it can be commercialized together with optically functional organic polymers, thereby increasing the long-term reliability of optical fiber. Also, since the polyorganosilsesquioxane prepared according to the present invention is used as a material for forming a coating on the surface of a resistor, it can be applied for electric/electronic materials.
Also, the polyorganosilsesquioxane prepared according to the present invention can be used as a metal release agent in plastic molding plastic, e.g., urethane reactive injection molding (RIM), or in manufacturing glass. Further, a mixture of RTV and the polyorganosilsesquioxane prepared according to the present invention can be used as a tile adhesive agent or outer surface coating of a space shuttle, a binder of optical fiber, and the like, and can be used for heat-resistive coating materials owing to its heat resistance and corrosion resistance.
The applicability of the final product according to the present invention will be boundlessly extended, not limited to the above-described fields, along with the development of advanced technology.
For better understanding of the present invention, the invention will now be described in detail through preferred embodiments with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, those embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.